Translations:Pyridoxal phosphate/21/en
The first branch is catalyzed in E. coli by enzymes encoded by epd, pdxB, serC and pdxA. These share mechanistical similarities and homology with the three enzymes in serine biosynthesis (serA (homologue of pdxB), serC, serB — however, epd is a homologue of gap), which points towards a shared evolutionary origin of the two pathways. In several species there are two homologues of the E. coli serC gene, generally one in a ser operon (serC), and the other in a pdx operon, in which case it is called pdxF.